全新java初学者实践教程6(Java SE5.0版)
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Lv/ 基本语法3
4id3P{aU i^je.,Bi tCWJSi`IJ 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
,3:QB_ 4-y6MH [font="Times] 1.循环语句[font="Times]:while,do-while,for
RI(=HzB "0|BoG [font="Times]2.分支语句[font="Times]:if-else,switch,
':,>eL#+uV [font="Times]
8W-]t1O%! 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
}US7Nw [font="Times]
uyL72($ 4.异常处理语句[font="Times]:try-catch-finally,throw
\4OK!6LkI B^Xy0fq 实践:
R `;o!B}[ [font="Times] 1.循环语句
dav vI$TA [font="Times] while 语句
k?^%hO>[ [font="Times]class While {
3QCMK^#Z: [font="Times]public static void main(String args[]) {
j: <t [font="Times]int n = 10;
q^u1z|'Z [font="Times]while(n > 0) {
Lb!r(o>8Cb [font="Times]System.out.println("tick " + n);
m+Y@UgB [font="Times]n--;
hgj CXl [font="Times]}
HKpD2M [font="Times]}
kfVZ=`p} [font="Times]}
0;vtdM[_ [font="Times] do…while 语句
)nhfkW=e [font="Times] class DoWhile {
rwoF}} [font="Times]public static void main(String args[]) {
q1UBKhpnH [font="Times]int n = 10;
--Oprl [font="Times]do {
gk"mr_03 [font="Times]System.out.println("tick " + n);
bKYY{V55 [font="Times]n--;
AvZXRN1:' [font="Times]} while(n > 0);
N].4"0Jv-D [font="Times]}
KZECo1 [font="Times]}
,SAbC*nq 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
LxB&7 [font="Times] for语句
l x7Kw% [font="Times] class ForTick {
^Ss<X}es- [font="Times]public static void main(String args[]) {
!@( M_Z' [font="Times]int n;
77``8, [font="Times]for(n=10; n>0; n--)
6!Qknk$ [font="Times]System.out.println("tick " + n);
AQ-mE9>P [font="Times]}
^ b@!dS [font="Times]}
?F1wh2oq 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
"s% 686Vz 还有啊,[font="Times]for循环的部分可以为空的
)eECOfmnZ [font="Times]class ForVar {
0X.TF [font="Times]public static void main(String args[]) {
+hpSxdAz4 [font="Times]int i;
0"TgLd [font="Times]boolean done = false;
Y7-*2"! [font="Times]i = 0;
NP "ylMr7P [font="Times]for( ; !done; ) {
6?O}Q7G [font="Times]System.out.println("i is " + i);
L4~
W/6A [font="Times]if(i == 10) done = true;
0k%hY{ [font="Times]i++;
'X54dXS?l [font="Times]}
}0Y`|H\v [font="Times]}
NJ<N %hcjK [font="Times]}
循环语句的例子下载 `y'aH
'EEd [font="Times] 2.分支语句[font="Times]
?<E0zM+ [font="Times] if/else语句
:aH%bk [font="Times]class IfElse {
MZ)T0|S_ [font="Times]public static void main(String args[]) {
AhR0zg [font="Times]int month = 4; // April
~,T+JX [font="Times]String season;
F% }7cm2 [font="Times]if(month == 12 || month == 1 || month == 2)
\Y9I~8\gB [font="Times]season = "Winter";
vuZf#\zh} [font="Times]else if(month == 3 || month == 4 || month == 5)
Y hS{$Z [font="Times]season = "Spring";
mzu<C)9d, [font="Times]else if(month == 6 || month == 7 || month == 8)
z<t>hzl7 [font="Times]season = "Summer";
<E SvvTf [font="Times]else if(month == 9 || month == 10 || month == 11)
w m19T7*L [font="Times]season = "Autumn";
mdaYYD=c% [font="Times]else
# J]~ [font="Times]season = "Bogus Month";
<iRWd [font="Times]System.out.println("April is in the " + season + ".");
X3AwM%,! [font="Times]}
zLL)VFCJW [font="Times]}
r( M[8@Nz [font="Times]//这段程序输出[font="Times]:
rfX=*mjt [font="Times]//April is in the Spring.
e^=NL>V6p [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
g*F~8+]Y [font="Times] switch语句
n6/f an; [font="Times] class Switch {
l/M[am [font="Times]public static void main(String args[]) {
5E`JD [font="Times]int month = 4;
ZEqE$: [font="Times]String season;
u7[pLtOwN [font="Times]switch (month) {
V;k#})_- [font="Times]case 12:
l**3%cTb [font="Times]case 1:
P0)AUi [font="Times]case 2:
0TmZ*?3!4 [font="Times]season = "Winter";
z#RuwB+ [font="Times]break;
2qlIy [font="Times]case 3:
{a.
<` [font="Times]case 4:
{gw[%[ZM [font="Times]case 5:
pD[pTMG@$ [font="Times]season = "Spring";
QhsVIta [font="Times]break;
-8/ JP
[font="Times]case 6:
rfc|`*m}0 [font="Times]case 7:
K>$qun?5 [font="Times]case 8:
/eb-'m [font="Times]season = "Summer";
!O 8.#+ [font="Times]break;
IhfZLE., [font="Times]case 9:
HJ",Sle [font="Times]case 10:
=6fB*bNk] [font="Times]case 11:
RbKwO}
z$q [font="Times]season = "Autumn";
bf(+ldq [font="Times]break;
a>w~FUm* [font="Times]default:
I )5<DZB9 [font="Times]season = "Bogus Month";
V,m3-=q [font="Times]}
xvB8YW" [font="Times]System.out.println("April is in the " + season + ".");
q=+wI"[ [font="Times]}
.'&V#D0 [font="Times]}
分支语句代码下载 "Vx6 #u@} 6`Lcs [font="Times]switch语句适合于条件非常多的逻辑
-zdmr"CA 请看上述语句可以混合使用,请看
下载例子